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To evaluate the effectiveness of teaching core tendon repairs using a simulation model, ten surgical residents with no prior experience repairing flexor tendons were taught a four-strand cruciate repair. The residents then performed ten repairs each on a simulated tendon (a round synthetic bait worm 10 mm in diameter) while being timed and graded by a hand surgeon using a global rating scale (1 to 5). Six residents also performed a zone IV flexor tendon repair on a fresh frozen cadaver—three residents who had practiced and three other residents who had no practice on the simulated tendon. The mean initial quality score was 2.4/5.0 which improved to 4.8/5.0 by the tenth trial. There was a significant incremental improvement in mean performance from trial 1 to 10 (p<0.0001). The mean times to complete the first and last repairs were 5.4 and 3.0 min, respectively. In the cadaver trial, there was statistically significant evidence (p=0.05, one-sided Wilcoxon exact test) that the three residents previously trained with the simulated tendon had a higher median performance (4.4, min=4.3, max=4.8) than the three who had not been trained (1.8, min=1.7, max=2.1). The mean times to complete the repairs were 4.0 and 5.8 min, respectively. In conclusion, this inexpensive model mimics an in vivo tendon repair experience with sufficient fidelity to justify its use in training residents to perform a tendon repair.
The training of surgical residents presents the challenge of teaching psychomotor skills on live patients. The early part of the learning curve fraught with errors and mistakes due to inexperience has real morbidity, yet inexperience can only be remedied by operating. Ensuring that this interface between trainee and patient occurs safely is one of the biggest responsibilities given to academic surgeons. Surgical simulation is therefore a necessary educational tool [5, 6, 11], allowing the trainee to develop technical skill sets without the added pressure and risk of learning or improving a technique on a living patient. Teaching a resident how to repair a flexor tendon is particularly difficult since the surgical skill is technically demanding, and ultimate function is directly proportionate to surgical skill; there is little room for error, but the learning surgeon commits many mistakes. Developing the fine motor skills needed to repair a tendon via surgical simulation while removed from the stress of the operating room is ideal and should enhance the trainee’s ability to focus on and combine those other aspects of being a well-rounded surgeon when in the operating room.
The purpose of this study was to evaluate the effectiveness of teaching residents how to repair a tendon using a simulation model designed to be efficient, simple, and inexpensive .
The study was conducted with the approval of the Institutional Review Board. Ten post-graduate, years 1 through 4 surgical residents with little or no prior experience repairing tendons, were taught how to perform a four-strand cruciate flexor tendon repair  by watching a 5-min instructional video. The video, created by the authors, showed a stepwise diagrammatic description of the repair. A single repair was then demonstrated using the simulated tendon (Fig. 1). The residents then performed ten repairs each on the simulated tendon while being timed and graded by a hand surgeon using a standardized checklist and global rating scale (Figs. 2 and and3)3) . The global rating scale contains nine categories; each category is graded on a scale from 1 to 5 ranging from “extremely poor” to “outstanding/mastery”, respectively. The majority of the residents accomplished their repairs in one to three sessions; one resident required four sessions. Three additional residents were not trained and did not practice on the simulated tendon.
The simulated tendon was a white, round, flexible, synthetic bait worm 10 mm in diameter and 6 cm long (Gary Yamamoto Custom Baits, Page, AZ, USA). The rubber worm was transected at its midpoint and pinned to a foam board taped securely to the underlying table. The residents used standard surgical instruments and a 4-0 monofilament suture for the repair. A reference diagram was placed adjacent to the repair station. When necessary, verbal guidance was given during the first repair only.
To assess the value of the simulated training experience, each resident was asked to evaluate the training exercise after the first repair. In addition, approximately 6 months later, six residents performed a single zone IV flexor tendon repair on a fresh frozen cadaver. Three residents were chosen at random from the ten who had simulation practice. The other three residents were those who had no simulation practice; they were given only a brief description of the repair technique (no video was shown) and active instruction as needed during the repair. All six residents could look at a repair diagram. They were timed and graded in the same manner as previously described.
All continuous variables of interest were summarized by trial using descriptive statistics (mean ± SD). The data on primary outcomes including mean performance was analyzed using a linear mixed model with trial effect (i.e., 1, 2,…, 10 trial) and group effect (group 1, all 10 trials were done on 1 day; group 2, all 10 trials were done on two different days; and group 3, all 10 trials were done on three or more different days) modeled as fixed effects; the ten residents were modeled as random effect.
Different correlation structures were tried in the model under the assumption that unequal time difference among trials had no effect on primary outcomes; the most appropriate model was chosen based on Akaike’s information criterion.
Two groups of residents, with and without previous training, were compared using the Wilcoxon exact test. A designated p value of 0.05 or less indicated a statistical significance, and SAS 9.1.3 (Cary, NC, USA) was used for data analysis.
All ten residents demonstrated improvement in repair time and quality over the course of ten repairs. Student performance as measured by the stepwise checklist increased for the first two repairs but then leveled off at 100% correct for the remainder of the repairs (Fig. 4). While the checklist did not provide any statistically meaningful data regarding resident improvement, the global rating scale did provide a valid assessment. The mean initial quality score using the global rating scale was 2.4/5.0 which improved to 4.8/5.0 by the tenth trial. There was a significant incremental improvement in mean performance from trial 1 to 10 (p<0.0001; Fig. 5) without clear evidence of leveling off before trial 9 where mean performance reached 4.6/5.0.
The mean time to complete the first repair was 5.4 min; this decreased to 3.0 min by the last repair (Fig. 6). There was a significant decreasing trend in completion time from trial 1 to 10 (p<0.0001). Three residents completed all ten trials in one sitting, and seven residents required two to four sittings; subjectively, it was observed that the latter group usually needed only one repair to recover their previous knowledge base before continuing with trends similar to the former group. The residents who worked with the simulated tendon stated that the experience was extremely useful and worthwhile (mean=4.9/5.0).
For the cadaver portion of the study, there was statistically significant evidence (p=0.05, one-sided Wilcoxon exact test) that the three residents who had previously been trained with the simulated tendon had a higher median performance (4.4, min=4.3, max=4.8) than the three who had not been trained (1.8, min=1.7, max=2.1). The median times to complete the repairs were 3.8 (min=3.5, max=4.6) and 5.5 min (min=5.3, max=6.7), respectively (p=0.05, one-sided Wilcoxon exact test).
Surgical simulation is a successful and important part of the modern surgical residency curriculum [1–4, 8–10]. To our knowledge, we are the first to report a surgical simulator designed to teach flexor tendon repairs. For such a simulation to be effective, it must express similarities to the actual operating room environment, have ease of application for novice users, be challenging enough for intermediate users, utilize effective assessment scales, and be transferable to the actual procedure being simulated.
A rubber bait worm serves as a good tendon simulator in its general appearance and feel. It is inexpensive and simple to set up. The fact that the model is more fragile than a real tendon is advantageous in helping the examiner assess for damage due to unnecessary or improper use of forceps, for example. From tendon handling to proper alignment to adequate tension in the repair, this model provides measurable steps. While actual flexor tendons are not round and are of smaller diameter than the simulated tendon, the latter still shares sufficient characteristics with the real-world counterpart to serve as a useful simulator. Other possible options for tendon repair practice would include cadaveric or animal sources; these options, while more authentic, are more expensive and labor intensive and less practical as a measurable teaching tool due to their variable size and consistency.
The global rating scale which was previously validated by a similar type of simulation study  served well to assess resident progress towards trial 10. The checklist, however, failed to distinguish progress because the residents tended to achieve 100% of the procedural steps early on in their number of repairs; thus, nothing further could be measured by the checklist. This trait was seen in other simulation models as well . Actual surgical repair time does not necessarily correlate with the quality of the flexor tendon repair. In this study, however, the repairs were timed to provide an independent means for demonstrating incremental improvement; this was shown to be statistically significant.
A weakness of this study was the non-standard number of repairs done per resident sitting. This was related to the logistics of coordinating with busy surgical residents and will largely be avoided when integrated into a standard teaching curriculum. A perceived weakness could pertain to the fact that the training video was not shown to the simulator-naive residents; this was purposefully done to better simulate an authentic operative setting in which training and operating often occur simultaneously. In the cadaver portion of the study, the one-sided Wilcoxon exact test provided significant results in comparing trained and untrained residents in performance and time to compete the repair; a sample size greater than three in each group would have been even more valuable.
The questions which remain are the following: What is the optimum number of simulated repairs needed to achieve a plateau in skills and efficiency? How often should such a simulator be utilized to maintain these skills? What other such simulators can we develop?
Employing this inexpensive-simulated tendon in teaching a repair technique allowed residents to perform their first repair on a cadaver more efficiently and with higher quality than those residents who did not practice on the simulated tendon. A total of ten simulated repairs per resident is sufficient and represents only 1 to 1.5 h of training time. Residents who trained with the simulated tendon have subsequently reported good confidence and minimal anxiety in performing their first true operative flexor tendon repair. This is gratifying evidence that we have achieved our intended goal: to provide a safer, more productive, and more efficient interface between the surgical resident and their first flexor tendon repair on a real patient.